Loop heat pipe

ABSTRACT

A loop heat pipe includes an evaporator and a tube hermetically connecting with the evaporator. The evaporator includes a metallic container and a first wick structure disposed on an inner surface of the container. The container defines a vapor outlet and a liquid inlet. The tube includes a vapor line connecting with the vapor outlet and a liquid line connecting with the liquid inlet of the evaporator. The vapor line and the liquid line of the tube communicate with each other. A second wick structure is adhered on a part of an inner surface of a wall of the tube and connects and communicates with the first wick structure at two opposite ends of the evaporator.

BACKGROUND

1. Technical Field

The present disclosure relates to heat pipes and, more particularly, to a loop heat pipe having a good heat dissipation efficiency and a stable and reliable performance.

2. Description of Related Art

Loop heat pipes have excellent heat transfer performance due to their low thermal resistance, and are therefore an effective means for transfer or dissipation of heat form heat-generating components such as central processing units (CPUs) of computers.

A conventional loop heat pipe comprises an evaporator thermally connected with a heat-generating component and disposing a wick structure therein, a condenser thermally connected with a heat sink, a vapor line and a liquid line disposed between and connecting the evaporator with the condenser. A predetermined quantity of bi-phase working medium is contained in the evaporator and the liquid line.

During operation of the loop heat pipe, the working medium in the wick structure of the evaporator absorbs heat from the heat-generated component and vaporizes. Thus, the vaporized working medium generates a vapor pressure which propels vaporized working medium towards the condenser via the vapor line. The vaporized working medium dissipates heat to the heat sink at the condenser and condenses to liquid thereat. The condensed working medium is then propelled through the liquid line and the evaporator in that order by the vapor pressure and by capillary action generated by the wick structure. Generally, each of the liquid line and the vapor line has a smooth, cylindrical configuration. When a little vaporized working medium condenses to liquid in the vapor line, the condensed working medium obstructs the vaporized working medium flows to the liquid line. Thus, a speed of the working medium flows back to the evaporator decreases. The evaporator is prone to be drying.

What is needed, therefore, is a loop heat pipe having a good heat dissipation efficiency and a stable and reliable performance.

BRIEF DESCRIPTION OF THE DRAWING

The sole drawing shows a cross-sectional view of a loop heat pipe in accordance with the present disclosure.

DETAILED DESCRIPTION

Referring to the sole drawing, it illustrates a loop heat pipe in accordance with the present disclosure. The loop heat pipe comprises an evaporator 10 and a tube 20 hermetically connects with the evaporator 10. A predetermined quantity of working medium (not labeled) is contained in the evaporator 10 and the tube 20. The working medium is a liquid which has a low boiling point such as water, methanol, or alcohol. Thus, the working medium can be easily evaporated to vapor when it absorbs heat transferred to the evaporator 10 and condensed to liquid when it dissipates heat to atmosphere.

The evaporator 10 comprises a container 11 and a porous elongated first wick structure 13 adhered on an inner surface of the container 11. The container 11 may be constructed from any suitable metallic, such as aluminum or stainless steel. In this embodiment, the first wick structure 13 and the container 11 each are preferably in a cylindrical shape.

The container 11 comprises a heat absorbing portion 112 and an extending portion 114 extending forwardly from a front end of the heat absorbing portion 112 along a central longitudinal axis of the heat absorbing portion 112. The heat absorbing portion 112 is used to thermally contact with a heat-generating component (not shown), such as a CPU (central processing unit) of a computer. A diameter of the extending portion 114 is larger than that of the heat absorbing portion 112. A vapor outlet 1121 is defined at a central portion of a rear end of the heat absorbing portion 112. A liquid inlet 1141 is defined at a central portion of a front end of the extending portion 114.

The first wick structure 13 consists of porous structure, such as screen mesh, or fiber inserted into the container 11 and held against the inner surface of the container 11, or sintered powders combined to the inner surface of the container 11 using a sintering process. The first wick structure 13 has a central longitudinal axis, which is coextensive with the central longitudinal axis of the heat absorbing portion 112 of the container 11. A receiving chamber 137 extends partially along the axis from an open end 134 to a closed end 132 of the first wick structure 13. The closed end 132 abuts against an inner surface of the rear end of the absorbing portion 112 of the container 11. The open end 134 abuts against an inner surface of the front end of the extending portion 114 of the container 11. The receiving chamber 137 comprises a first chamber 1371 and a second chamber 1373 communicating with the first chamber 1371. The first chamber 1371 is near to the closed end 132 of the first wick structure 13. The second chamber 1373 is near to the opening end 134 of the first wick structure 13. A diameter of the second chamber 1373 is larger than that of the first chamber 1371. The second chamber 1373 is a compensation chamber for supplying liquid working medium to the first chamber 1371.

Opposite ends of the tube 20 connect with the vapor outlet 1121 and the liquid inlet 1141 of the evaporator 11, respectively. The tube 20 is made of metallic materials compatible with the working medium, such as aluminum, stainless steel. The tube 20 can be easily bent and deformed to a desired configuration. A continuous second wick structure 24 is adhered on a part of an inner face of a wall of the tube 20. Opposite ends of the second wick structure 24 connect and communicate with the close end 132 and the open end 134 of the first wick structure 13 of the evaporator 11. The tube 20 comprises a vapor line 21 and a liquid line 22 communicating with the vapor line 21. Opposite ends of the vapor line 21 connect with the vapor outlet 1121 and the liquid line 22, respectively. The vaporized working medium flows through the vapor line 21 towards the liquid line 22. Opposite ends of the liquid line 22 connect with the liquid inlet 1141 and the vapor line 21, respectively. The liquid working medium flows through the liquid line 22 toward the liquid inlet 1141 of the evaporator 10. The second wick structure 24 absorbs condensed working medium in the vapor line 21 and guides the condensed working medium into the evaporator 11 from the liquid inlet 1141 of the evaporator 11.

During operation of the loop heat pipe, the working medium in the first wick structure 13 absorbs heat from the heat-generating component and vaporizes. The vapor pressure of the vaporized working medium expels the vaporized working medium to flow through the vapor line 21 via the vapor outlet 1121. The second wick structure 24 absorbs condensed working medium, if any, in the vapor line 21 to prevent the obstruction of flowing of the vaporized working medium in the vapor line 21 by the condensed working medium. The vaporized working medium dissipates the heat via the tube 20 and condenses to liquid thereat. The condensed working medium is then propelled through the liquid line 22, the second chamber 1373 and the first chamber 1371 of the receiving chamber 137 in that order by the capillary action generated by the second and first wick structures 24, 13. The condensed working medium at the evaporator 10 then evaporates into vapor again to start another heat transfer cycle. A heat absorbing plate 30 thermally contacts with the vapor line 21 to absorb heat of the vaporized working medium thereby dissipating heat of the heat-generating component to the atmosphere. The heat absorbing plate 30 functions as a heat sink. Although it is not shown, it is readily appreciated by those skilled in the art that the heat absorbing plate 30 can be provided with fins for increasing the heat dissipation efficiency.

It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the disclosure, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A loop heat pipe comprising: an evaporator comprising a metallic container and a first wick structure disposed on an inner surface of the container, the container defined a vapor outlet and a liquid inlet; and a tube hermetically connecting with the vapor outlet and the liquid inlet of the evaporator, the tube comprising a vapor line connecting with the vapor outlet and a liquid line connecting with the liquid inlet, the vapor line and the liquid line communicating with each other; wherein a second wick structure is disposed on an inner surface of a wall of the vapor line and connects and communicates with the first wick structure.
 2. The loop heat pipe as claimed in claim 1, wherein the second wick structure is continuous and disposed on a part of the inner surface of the wall of the vapor line.
 3. The loop heat pipe as claimed in claim 2, wherein the second wick structure is continuous and also disposed on a part of an inner surface of a wall of the liquid line.
 4. The loop heat pipe as claimed in claim 3, wherein opposite ends of the second wick structure connect and communicate with the first wick structure.
 5. The loop heat pipe as claimed in claim 3, wherein each of the first and second wick structures consists of one of screen mesh, fiber and sintered powders.
 6. The loop heat pipe as claimed in claim 1, wherein the container of the evaporator comprises a heat absorbing portion and an extending portion extending outwardly from a lateral end of the heat absorbing portion, and the extending portion is larger than the heat absorbing portion.
 7. The loop heat pipe as claimed in claim 6, wherein the first wick structure has a closed end abutting against the inner surface of the container at which the vapor outlet is located, and an opening end abutting against the inner surface of the container at which the liquid inlet is located.
 8. The loop heat pipe as claimed in claim 7, wherein a receiving chamber is defined in the central portion of the first wick portion along a longitudinal direction of the central portion to receive liquid working medium therein.
 9. The loop heat pipe as claimed in claim 1 further comprising a heat sink contacting with the vapor line of the tube. 